1. Field of the Invention
The present invention generally relates to an image forming copying apparatus such as a copying machine or a printer or the like.
2. Description of the Related Art
In a sort of the image forming apparatus such as an electrophotographic copying machine, an operation panel is usually provided for operating the apparatus, such as changing a copy quantity, a magnification, and an exposure level, or selecting a simplex copy, a duplex copy and/or a composite copy. Furthermore, keys, such as ten-keys, rotation keys, each of which changes states or modes assigned thereto successively and cyclically each depressing thereof, and UP-and DOWN-keys, for doing decision whether a sorter can be used or not are arranged on the operation panel. An operator operates these keys in order to set a various kind of operation mode for copying. On the other hand, apparatuses are available, which are provided with a variable resistor for setting the copy quantity and/or an image density by an operation of sliding or rotating.
For example, the above-mentioned apparatuses with the different arrangements can be found in U.S. Pat. No. 4,320,964, issued on Mar. 23, 1982, U.S. Pat. No. 4,393,375, issued on July 12, 1983, U.S. Pat. No. 4,394,087, issued on July 19, 1983, and U.S. Pat. No. 4,564,287, issued on Jan. 14, 1986.
Although the above-mentioned apparatuses are put to practical use and are under operating, the apparatus having ten-keys for setting the magnification, for example, has a following disadvantage from the point of operational view. That is, in case of setting a suitable magnification with trail and error, an operator must take a key-operation for inputting a new magnification value every time when the magnification would be changed. Therefore, a fine adjustment for a clear copy is very difficult as well as an altering operation is troublesome. In case of setting the magnification with the rotation keys and/or UP- and DOWN-keys, some apparatuses having a setting range of the magnification, which is arranged stepwise have a disadvantage that the setting operation can not be done smoothly.
On the other hand, in accommodating the variable resistor in the apparatus, an adjusting range of the magnification is limited, besides there is a disadvantage that it is necessary to return to a standard position mechanically in the case of automatic resetting or the like since an input value for setting the magnification is an absolute value measured from the standard position.
Furthermore, there is a further disadvantage for the above-mentioned apparatus that a key operation is to be troublesome as well as to get easily into a wrong operation since a different key applies to a different operation mode, i.e., the ten-keys for setting copy quantity, and the rotation key and/or UP- and DOWN-keys for setting the magnification. In other words, respective operations are carried out with corresponding keys.